Located in the Diablo Mountains just west of I5, about 50 miles from Fresno, the long abandoned operation has become a source of mercury contamination, posing a threat to people and wildlife.
Nearly a decade after Action News first took you to New Idria. Reporter Gene Haagenson returned to the mine to see how the federal government is just starting to clean up a toxic legacy.
New Idria, California was founded back in 1854. Now a ghost town it was once a thriving community, surrounding the world's second largest mercury mine and smelter. Not much has been going on here since it all shut down, in 1970. But things are starting to happen.
Local resident, Kemp Woods said, "They're tackling a big problem that's been needed to be tackled for a long time."
Woods lives just down the road, he and his sister Kate fought for 30 years to get the government to deal with the mercury contamination this operation left behind. He's glad the EPA has finally come calling.
Rusty Harris-Bishop with the EPA said, "So this is something we have determined is a priority that we can put some effort and funding to clean up."
The Environmental Protection Agency has declared this a superfund site. Meaning it's among the most polluted sites in the country. While the government has long been aware of the hazards, this isolated site was not a priority, until research showed the danger was spreading.
Kelly Manheimer with the EPA said, "Mercury really does get transported pretty far off site, and even at this site we were seeing mercury in detectable amounts, substantial amounts 40 miles downstream from this site, so that's pretty far."
The contamination flows into San Carlos Creek, and the water eventually meanders into the Central Valley and the San Joaquin River.
In wet years the poison could be carried into the Sacramento Delta, even San Francisco Bay. EPA scientist Kelly Manheimer says the mercury can be a threat to all living things along the way.
Manheimer said, "We realized a lot of things happened to mercury it becomes methylated it turns into a different form of mercury."
Once absorbed by fish mercury becomes more toxic as it moves through the food chain. In people, mercury poisoning damages the brain and nervous system. Many New Idria miners are believed to have suffered from mercury poisoning.
Action News first visited New Idria in 2004. A stream of water containing sulfuric acid, mercury, iron and other metals spewed out of the mine opening picking up even more mercury from the ore left on the ground.
Cleanup started late last year. Now, the opening has been filled, the water diverted underground into a pipe, and into a settling pond. A quick first step.
Manheimer said, "That's one reason I wanted to jump in and take that action. Because I knew it would have an immediate effect."
The water coming out of the mine is still orange and it's still not healthy. The EPA may have to build a treatment plant here to clean it up even more.
New Idria is more than a toxic leftover from days gone by. Larry Lopez owns the Panoche Inn, about 30 miles from the old town. He's collected artifacts from the old mining days.
Lopez said, "To think there were generations of people, that lived there, not just a few miners that came and went, they actually lived there, they had their children, that alone is a historical wealth."
During it's more than one hundred years of production, mercury from New Idria was used in gold processing, military weapons, electrical equipment, nuclear reactors and dental fillings.
During its peak years New Idria produced mercury that would be worth about $20 million today. But the cost of cleaning up could be up to $10 million. Half a million has been spent so far.
Kemp Woods thinks it is money well spent.
"My hats are off to the EPA, I know a lot of people have gripes with the EPA but they do some good work," said Woods. "They do good work and I can think of a lot of dollars that are spent a lot worse."
In addition to cleaning up, the EPA will be doing extensive studies to find out how much contamination is here how far it's spread, and just how dangerous it might be.